Clinicopathological and genetic features of anastomosing haemangioma of the kidney: a narrative review

: Anastomosing haemangioma of the kidney is a benign vascular neoplasm composed of thin-walled anastomosing blood vessels. Anastomosing haemangiomas are exceptionally rare. Approximately 75 cases have been described in the literature. The mean age of patients at diagnosis is 49 years (range, 10–83 years). There is a slight male predominance with a male-to-female ratio of 2:1. Patients present with non-specific symptoms including abdominal pain, haematuria, and abdominal mass. Anastomosing haemangiomas are spongy and well circumscribed mahogany brown masses without necrosis. These tumours are usually unilateral and solitary. Microscopically, the tumours are composed of anastomosing capillary-sized blood vessels lined by a single layer of bland endothelial cells. Anastomosing haemangiomas are positive for ERG, CD31, CD34, factor VIII-related antigen and FLI1. These tumours harbour recurrent somatic mutations in the GNAQ gene and its paralogue, GNA14. The considerable overlap of clinical features and imaging characteristics between anastomosing haemangioma and other vascular tumours of the kidney, particularly primary renal angiosarcoma, makes diagnosis quite challenging. Unlike primary renal angiosarcoma, anastomosing haemangioma has an excellent prognosis with no risk of recurrence or metastasis. For this reason, anastomosing haemangioma must be distinguished from primary renal angiosarcoma. Awareness of anastomosing haemangioma of the kidney is essential to avoiding misdiagnosis of primary renal angiosarcoma and preventing unnecessary aggressive treatment.